Rotating heat exchanger with tube coil

ABSTRACT

A heat exchanger includes a cylindrical stator and a cylindrical rotor that are spaced by a cylindrical gap. The cylindrical rotor is configured to rotate relative to the cylindrical stator about a rotation axis. A flattened tube is positioned within the cylindrical gap and is wrapped on the cylindrical stator. The flattened tube is spaced from a surface of the cylindrical rotor that faces the cylindrical gap.

FIELD OF THE INVENTION

The present subject matter relates generally to heat exchangers.

BACKGROUND OF THE INVENTION

Certain appliances use sealed refrigeration systems to cool portions of the appliance. For instance, refrigerator appliances generally include a cabinet that defines a chilled chamber that is often cooled with a sealed refrigeration system. Evaporators that incorporate fins, blades, or plates conduct heat between an ambient environment and a refrigerant fluid flowing through the sealed refrigeration system.

The efficacy and efficiency of a sealed refrigeration system may be, at least in part, contingent on the amount of heat that can be exchanged at the evaporator. However, many existing systems struggle to consistently exchange adequate amounts of heat to/from the evaporator. Moreover, certain systems, such as those utilizing multiple static blades to improve heat exchange, require significant amounts of space in order for their corresponding heat-exchange features to be effective. In the case of a system that uses a blower or fan, the rotation of the fan may generate significant amounts of undesirable noise. These constraints can limit the usability of the overall appliance. For instance, in the case of refrigerator appliances, the increased space needed for the heat-exchange elements naturally limits the potential size of other portions of the appliance, such as the chilled chamber. The noise generated by one or more fans may limit the areas in which a user may want to install the appliance.

BRIEF DESCRIPTION OF THE INVENTION

Aspects and advantages of the invention will be set forth in part in the following description, or may be apparent from the description, or may be learned through practice of the invention.

In a first example embodiment, a heat exchanger includes a cylindrical stator. A cylindrical rotor is spaced from the cylindrical stator by a cylindrical gap. The cylindrical rotor is configured to rotate relative to the cylindrical stator about a rotation axis. A flattened tube is positioned within the cylindrical gap and is wrapped on the cylindrical stator. The flattened tube is spaced from a surface of the cylindrical rotor that faces the cylindrical gap. A heat transfer fluid is flowable through the flattened tube. A shearing liquid zone is defined between the flattened tube and the surface of the cylindrical rotor when the cylindrical gap is filled with a liquid.

In a second example embodiment, an appliance includes a cabinet that defines a chilled chamber. A heat exchanger is positioned within the cabinet. The heat exchanger includes a cylindrical stator. A cylindrical rotor is spaced from the cylindrical stator by a cylindrical gap. The cylindrical rotor is configured to rotate relative to the cylindrical stator about a rotation axis. A flattened tube is positioned within the cylindrical gap and is wrapped on the cylindrical stator. The flattened tube is spaced from a surface of the cylindrical rotor that faces the cylindrical gap. A heat transfer fluid is flowable through the flattened tube. A shearing liquid zone is defined between the flattened tube and the surface of the cylindrical rotor when the cylindrical gap is filled with a liquid.

These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures.

FIG. 1 is a front perspective view of a refrigerator appliance according to an example embodiment of the present disclosure.

FIG. 2 is a schematic view of various components of the example refrigerator appliance of FIG. 1.

FIG. 3 is a section view of a heat exchanger according to an example embodiment of the present disclosure.

FIGS. 4 and 5 are schematic views of various components of the example heat exchanger of FIG. 3.

FIG. 6 is a section view of a heat exchanger according to another example embodiment of the present disclosure.

DETAILED DESCRIPTION

Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.

FIG. 1 provides a front view of a representative refrigerator appliance 10 according to an example embodiment of the present disclosure. More specifically, for illustrative purposes, the present disclosure is described in the context of a refrigerator appliance 10 having a construction as shown and described further below. As used herein, a refrigerator appliance includes appliances such as a refrigerator/freezer combination, side-by-side, bottom mount, compact, and any other style or model of refrigerator appliance. Accordingly, other configurations including multiple and different styled compartments may be used with refrigerator appliance 10, it being understood that the configuration shown in FIG. 1 is provided by way of example only.

Refrigerator appliance 10 includes a fresh food storage compartment 12 and a freezer storage compartment 14. In this embodiment, freezer compartment 14 and fresh food compartment 12 are arranged side-by-side within an outer case 16 and defined by inner liners 18 and 20 therein. A space between case 16 and liners 18, 20 and between liners 18, 20 may be filled with foamed-in-place insulation. Outer case 16 normally is formed by folding a sheet of a suitable material, such as pre-painted steel, into an inverted U-shape to form the top and side walls of case 16. A bottom wall of case 16 normally is formed separately and attached to the case side walls and to a bottom frame that provides support for refrigerator appliance 10. Inner liners 18 and 20 are molded from a suitable plastic material to form freezer compartment 14 and fresh food compartment 12, respectively. Alternatively, liners 18, 20 may be formed by bending and welding a sheet of a suitable metal, such as steel.

A breaker strip 22 extends between a case front flange and outer front edges of liners 18, 20. Breaker strip 22 is formed from a suitable resilient material, such as an extruded acrylo-butadiene-styrene based material (commonly referred to as ABS). The insulation in the space between liners 18, 20 is covered by another strip of suitable resilient material, which also commonly is referred to as a mullion 24. In one embodiment, mullion 24 is formed of an extruded ABS material. Breaker strip 22 and mullion 24 form a front face, and extend completely around inner peripheral edges of case 16 and vertically between liners 18, 20. Mullion 24, insulation between compartments, and a spaced wall of liners separating compartments, sometimes are collectively referred to herein as a center mullion wall 26. In addition, refrigerator appliance 10 includes shelves 28 and slide-out storage drawers 30, sometimes referred to as storage pans, which normally are provided in fresh food compartment 12 to support items being stored therein.

Refrigerator appliance 10 can be operated by one or more controllers 11 or other processing devices according to programming or user preference via manipulation of a control interface 32 mounted (e.g., in an upper region of fresh food storage compartment 12 and connected with controller 11). Controller 11 may include one or more memory devices (e.g., non-transitive memory) and one or more microprocessors, such as a general or special purpose microprocessor operable to execute programming instructions or micro-control code associated with the operation of the refrigerator appliance 10. The memory may represent random access memory such as DRAM, or read only memory such as ROM or FLASH. In one embodiment, the processor executes programming instructions stored in memory. The memory may be a separate component from the processor or may be included onboard within the processor. Controller 11 may include one or more proportional-integral (“PI”) controllers programmed, equipped, or configured to operate the refrigerator appliance according to various control methods. Accordingly, as used herein, “controller” includes the singular and plural forms.

Controller 11 may be positioned in a variety of locations throughout refrigerator appliance 10. In the illustrated embodiment, controller 11 may be located, for example, behind an interface panel 32 or doors 42 or 44. Input/output (“I/O”) signals may be routed between the control system and various operational components of refrigerator appliance 10 along wiring harnesses that may be routed through, for example, the back, sides, or mullion 26. Typically, through user interface panel 32, a user may select various operational features and modes and monitor the operation of refrigerator appliance 10. In one embodiment, the user interface panel 32 may represent a general purpose I/O (“GPIO”) device or functional block. In one embodiment, the user interface panel 32 may include input components, such as one or more of a variety of electrical, mechanical or electro-mechanical input devices including rotary dials, push buttons, and touch pads. The user interface panel 32 may include a display component, such as a digital or analog display device designed to provide operational feedback to a user. User interface panel 32 may be in communication with controller 11 via one or more signal lines or shared communication busses.

In some embodiments, one or more temperature sensors are provided to measure the temperature in the fresh food compartment 12 and the temperature in the freezer compartment 14. For example, first temperature sensor 52 may be disposed in the fresh food compartment 12 and may measure the temperature in the fresh food compartment 12. Second temperature sensor 54 may be disposed in the freezer compartment 14 and may measure the temperature in the freezer compartment 14. This temperature information can be provided (e.g., to controller 11 for use in operating refrigerator 10). These temperature measurements may be taken intermittently or continuously during operation of the appliance or execution of a control system.

Optionally, a shelf 34 and wire baskets 36 may be provided in freezer compartment 14. Additionally or alternatively, an ice maker 38 may be provided in freezer compartment 14. A freezer door 42 and a fresh food door 44 close access openings to freezer and fresh food compartments 14, 12, respectively. Each door 42, 44 is mounted to rotate about its outer vertical edge between an open position, as shown in FIG. 1, and a closed position (not shown) closing the associated storage compartment. In alternative embodiments, one or both doors 42, 44 may be slidable or otherwise movable between open and closed positions. Freezer door 42 includes a plurality of storage shelves 46, and fresh food door 44 includes a plurality of storage shelves 48.

Referring now to FIG. 2, refrigerator appliance 10 may include a refrigeration system 200. In general, refrigeration system 200 is charged with a refrigerant that is flowed through various components and facilitates cooling of the fresh food compartment 12 and the freezer compartment 14. Refrigeration system 200 may be charged or filled with any suitable refrigerant. For example, refrigeration system 200 may be charged with a flammable refrigerant, such as R441A, R600a, isobutene, isobutane, etc.

Refrigeration system 200 includes a compressor 202 for compressing the refrigerant, thus raising the temperature and pressure of the refrigerant. Compressor 202 may for example be a variable speed compressor, such that the speed of the compressor 202 can be varied between zero percent (0%) and one hundred percent (100%) by controller 11. Refrigeration system 200 may further include a condenser 204, which may be disposed downstream of compressor 202 in the direction of flow of the refrigerant. Thus, condenser 204 may receive refrigerant from the compressor 202, and may condense the refrigerant by lowering the temperature of the refrigerant flowing therethrough due to, for example, heat exchange with ambient air).

Refrigeration system 200 further includes an evaporator 210 disposed downstream of the condenser 204. Additionally, an expansion device 208 may be utilized to expand the refrigerant—thus further reducing the pressure of the refrigerant—leaving condenser 204 before being flowed to evaporator 210. Evaporator 210 generally transfers heat from ambient air passing over the evaporator 210 to refrigerant flowing through evaporator 210, thereby cooling the air and causing the refrigerant to vaporize. An evaporator fan 212 may be used to force air over evaporator 210 as illustrated. As such, cooled air is produced and supplied to refrigerated compartments 12, 14 of refrigerator appliance 10. In certain embodiments, evaporator fan 212 can be a variable speed evaporator fan, such that the speed of fan 212 may be controlled or set anywhere between and including, for example, zero percent (0%) and one hundred percent (100%). The speed of evaporator fan 212 can be determined by, and communicated to, evaporator fan 212 by controller 11.

Turning now to FIGS. 3 through 5, a heat exchanger 100 according to an example embodiment of the present disclosure is discussed in greater detail below. Heat exchanger 100 may be used in refrigerator appliance 10, e.g., as condenser 204 and/or evaporator 210. Thus, heat exchanger 100 is described in greater detail below in the context of refrigerator appliance 10. However, it will be understood that heat exchanger 100 may be used in or with any suitable appliance in alternative example embodiments. For example, heat exchanger 100 may be used in a heat pump water heater, a heat pump dryer, an HVAC unit, etc. Heat exchanger 100 may define an axial direction A and a radial direction R that are perpendicular to each other.

As shown in FIG. 3, heat exchanger 100 includes a cylindrical stator 110 and a cylindrical rotor 120. Cylindrical stator 110 and cylindrical rotor 120 may collectively form a hub 102 of heat exchanger 100. Cylindrical rotor 120 is spaced from cylindrical stator 110 by a cylindrical gap 130. Thus, e.g., cylindrical rotor 120 may not contact cylindrical stator 110 at cylindrical gap 130. Cylindrical rotor 120 is configured to rotate about a rotation axis X relative to cylindrical stator 110. The rotation axis X may be parallel to the axial direction A and perpendicular to the radial direction R. To rotate cylindrical rotor 120, heat exchanger 100 may include a motor 140. Motor 140 is coupled to cylindrical rotor 120 such that motor 140 is operable to rotate cylindrical rotor 120 about the rotation axis X.

Motor 140 may be a variable speed motor. Thus, e.g., a rotation speed of cylindrical rotor 120 about the rotation axis X may be adjusted by changing the speed of motor 140. Controller 11 may be in operative communication with motor 140, and controller 11 may be operable to adjust the speed of motor 140. The speed of motor 140 may be controlled or set anywhere between and including, for example, zero percent (0%) and one hundred percent (100%). As a particular example, motor 140 may be operable to adjust the rotation speed of cylindrical rotor 120 about the rotation axis X to any suitable speed no less than two hundred and fifty rotations per minute (250 RPM) and no greater than two thousand, five hundred rotations per minute (2500 RPM).

In FIG. 3, cylindrical stator 110 is positioned within cylindrical rotor 120. In particular, cylindrical stator 110 is positioned inside cylindrical rotor 120 and is positioned coaxial with cylindrical rotor 120. It will be understood that the relative position of cylindrical stator 110 and cylindrical rotor 120 may be reversed in alternative example embodiments. Thus, e.g., cylindrical rotor 120 may be positioned within cylindrical stator 110 in alternative example embodiments.

In FIG. 3, motor 140 is also positioned within cylindrical stator 110. For example, motor 140 may be positioned within an internal volume 114 of cylindrical stator 110. Internal volume 114 may be positioned opposite cylindrical gap 130 about cylindrical stator 110 along the radial direction R. A shaft 142 of motor 140 may extend, e.g., along an axial direction A, through an end wall 116 of cylindrical stator 110 from internal volume 114. Cylindrical rotor 120 is coupled to shaft 142 of motor 140. Thus, motor 140 may be operable to rotate cylindrical rotor 120 about the rotation axis X from within cylindrical stator 110. An O-ring 118 or other suitable seal may extend between the shaft 142 of motor 140 and end wall 116 of cylindrical stator 110. O-ring 118 may block liquid flow into internal volume 114 via the interface between shaft 142 of motor 140 and end wall 116 of cylindrical stator 110. In alternative example embodiments, motor 140 may be positioned externally of cylindrical stator 110, and cylindrical rotor 120 may be driven by motor 140 through gears or a belt/pulley.

A flattened tube 150 is positioned within cylindrical gap 130, and flattened tube 150 is wrapped on cylindrical stator 110, e.g., such that flattened tube 150 is coiled around cylindrical stator 110. Thus, cylindrical rotor 120 may rotate relative to flattened tube 150 during operation of motor 140. Flattened tube 150 is also spaced from a surface 122 of cylindrical rotor 120, e.g., along a radial direction R. Surface 122 of cylindrical rotor 120 faces cylindrical gap 130. In FIG. 3, surface 122 of cylindrical rotor 120 is an inner surface of cylindrical rotor 120, and flattened tube 150 is wound onto an outer surface 112 of cylindrical stator 110. As shown in FIG. 3, flattened tube 150 may be wound onto outer surface 112 of cylindrical stator 110 in one or more layers. A heat transfer fluid, such as a refrigerant, is flowable through flattened tube 150.

Cylindrical gap 130 may be filled with a liquid, such as water, propylene glycol, etc., and the liquid may facilitate heat transfer along the radial direction R within cylindrical gap 130 between cylindrical rotor 120 and flattened tube 150. For example, the liquid in cylindrical gap 130 may facilitate conductive heat transfer between cylindrical rotor 120 and flattened tube 150, e.g., relative to cylindrical gap 130 being filled with a gas, such as air. Thus, the liquid in cylindrical gap 130 may contact both cylindrical rotor 120 and flattened tube 150 within cylindrical gap 130, and the liquid may correspond to a heat transfer fluid between cylindrical rotor 120 and flattened tube 150 within cylindrical gap 130.

In addition, a shearing liquid zone 160 is defined between flattened tube 150 and surface 122 of cylindrical rotor 120. Thus, shearing liquid zone 160 may correspond to the portion of cylindrical gap 130 positioned between surface 122 of cylindrical rotor 120 and flattened tube 150, e.g., along the radial direction R. Liquid within shearing liquid zone 160 may shear during rotation of cylindrical rotor 120 relative to cylindrical stator 110, and shearing of the liquid may facilitate convective heat transfer between cylindrical rotor 120 and flattened tube 150 via the liquid.

By positioning flattened tube 150 within cylindrical gap 130, heat exchanger 100 may be produced in a more cost effective manner relative to known heat exchangers that require complex flow circuits. In addition, a size of heat exchanger 100 may be reduced relative to known heat exchangers. For example, heat exchanger 100 may be about half the size of known heat exchangers with similar heat transfer characteristics and that require, e.g., a fan, shroud, spine fins, etc.

Convection heat transfer within cylindrical gap 130 increases with shear rate. Thus, changing the rotational speed of cylindrical rotor 120 about the rotation axis X (e.g., by varying the speed of motor 140 in the manner described above) may likewise change the convection heat transfer along the radial direction R within cylindrical gap 130 between cylindrical rotor 120 and flattened tube 150. In particular, increasing the rotational speed of cylindrical rotor 120 about the rotation axis X may increase convection heat transfer along the radial direction R within cylindrical gap 130 between cylindrical rotor 120 and flattened tube 150. Conversely, decreasing the rotational speed of cylindrical rotor 120 about the rotation axis X may decrease convection heat transfer along the radial direction R within cylindrical gap 130 between cylindrical rotor 120 and flattened tube 150.

Turning to FIG. 4, flattened tube 150 may have a flat or planar surface 152. Thus, e.g., flattened tube 150 may have a non-circular cross-section. In FIG. 4, flattened tube 150 has a square cross-section. In alternative example embodiments, flattened tube 150 may have a stadium shaped cross-section, a rectangular cross-section, etc. As an example, flattened tube 150 may be formed by rolling a circular metal tube to form flat surface 152. Thus, flattened tube 150 may be a rolled metal tube.

Flat surface 152 of flattened tube 150 may face surface 122 of cylindrical rotor 120 across shearing liquid zone 160. Thus, e.g., flat surface 152 of flattened tube 150 may correspond to a static shear surface of shearing liquid zone 160, and surface 122 of cylindrical rotor 120 may correspond to a dynamic shear surface of shearing liquid zone 160. Flat surface 152 of flattened tube 150 may be oriented parallel to surface 122 of cylindrical rotor 120 across shearing liquid zone 160.

A thickness T of shearing liquid zone 160 may be defined between flat surface 152 of flattened tube 150 and surface 122 of cylindrical rotor 120 along the radial direction R. In certain example embodiments, the thickness T of shearing liquid zone 160 may be no less than about one hundredth of an inch (0.01 inch) and no greater than about one tenth of an inch (0.1 inch). As used herein, the term “about” means within ten percent of the stated thickness when used in the context of thicknesses. By utilizing flattened tube 150, the thickness T of shearing liquid zone 160 may be more consistent or uniform relative to circular tubes. In addition, heat exchanger 100 may be formed with the size of the thickness T of shearing liquid zone 160 decreased relative to using circular tubes by using flattened tube 150.

Flattened tube 150 may provide a single flow path for heat transfer fluid. However, in certain example embodiments, heat exchanger 100 includes multiple flattened tubes 150. For example, as shown in FIG. 4, heat exchanger 100 may include a first flattened tube 152 and a second flattened tube 154. First and second flattened tubes 152, 154 are both positioned within cylindrical gap 130 and wrapped on cylindrical stator 110. First and second flattened tubes 152, 154 may be plumbed in parallel within refrigeration system 200 such that first and second flattened tubes 152, 154 each define a respective flow path for heat transfer fluid with heat exchanger 100.

With reference to FIGS. 3 and 5, heat exchanger 100 may include a fan 170. Fan 170 may include a plurality of spaced planar fins 172. Spaced planar fins 172 extend from cylindrical rotor 120, e.g., outwardly along the radial direction R. Cylindrical rotor 120 may for formed of or with a suitable thermally conductive material. For example, cylindrical rotor 120 may be formed from one or more conductive materials, such as aluminum, copper, or tin, as well as alloys thereof. Each planar fin 172 is in conductive thermal communication with cylindrical rotor 120. For example, planar fins 172 may directly contact cylindrical rotor 120. In certain example embodiments, spaced planar fins 172 are separably attached to (e.g., in direct or indirect contact with) cylindrical rotor 120 (e.g., as discrete removable discs). Spaced planar fins 172 may also be formed from a conductive material that is the same or different from the material of cylindrical rotor 120. For instance, spaced planar fins 172 may be formed from stainless steel, aluminum, copper, or tin, as well as alloys thereof.

Spaced planar fins 172 define one or more axial intake channels 174. Axial intake channels 174 may extends through one or more planar fins of spaced planar fins 172, e.g., parallel to the rotation axis X and/or along the axial direction A. Each of the axial intake channels 174 may be positioned at a common radial distance from the rotation axis X.

Spaced planar fins 172 are mounted to cylindrical rotor 120, e.g., such that spaced planar fins 172 rotate with cylindrical rotor 120 about the rotation axis X. As spaced planar fins 172 rotate, fan 170 operates in a manner similar to a so called “Tesla fan.” Turning to FIG. 5, an airflow (shown with arrows AF) may be drawn along the axial direction A into axial intake channels 174 when spaced planar fins 172 rotate about the rotation axis X. The airflow AF may flows into axial intake channels 174 from opposite axial ends spaced planar fins 172. Within spaced planar fins 172, the airflow AF passes from axial intake channels 174 to one or more exhaust channels defined between adjacent spaced planar fins 172. The exhaust channels may correspond to axial gaps between adjacent spaced planar fins 172.

From the exhaust channels, the airflow AF is directed outwardly along the radial direction R between spaced planar fins 172 before being exhausted from heat exchanger 100. Advantageously, heat exchanger 100 may promote a heat exchange between spaced planar fins 172 and airflow AF without generating the noise associated with, for example, an axial blower fan. Thus, e.g., spaced planar fins 172 may reject heat to the airflow AF during operation of heat exchanger 100 when heat exchanger 100 is used as condenser 204. Alternatively, e.g., the airflow AF may reject heat to spaced planar fins 172 during operation of heat exchanger 100 when heat exchanger 100 is used as evaporator 210.

As spaced planar fins 172 rotate, viscous forces add energy to the airflow AF between spaced planar fins 172. The boundary layer on spaced planar fins 172 may drive the airflow AF outwardly along the radial direction R. The spacing along the axial direction A between adjacent spaced planar fins 172 may be selected to facilitate driving of the airflow AF outwardly along the radial direction R between spaced planar fins 172. For example, each spaced planar fin 172 may be spaced from an adjacent spaced planar fin 172 along the axial direction A by no more than about twenty-five micrometers (25 μm). Such spacing may permit operation of fan 170 in the manner described above in certain example embodiments.

As shown in FIG. 6, cylindrical stator 110 may include fins or corrugations 124 that project outwardly along the radial direction R. Flattened tube 150 may be positioned on distal ends of corrugations 124. Spaces or gaps between adjacent corrugations 124 may provide a flow path for liquid, e.g., along the axial direction A, between cylindrical stator 110 and flattened tube 150. Thus, liquid in cylindrical gap 130 may flow within the spaces between adjacent corrugations 124, and the liquid between adjacent corrugations 124 may increase convection heat transfer along the radial direction R within cylindrical gap 130 between cylindrical rotor 120 and flattened tube 150 relative to cylindrical stator 110 without corrugations 124.

Cylindrical rotor 120 may include fins or corrugations 119 that project outwardly along the radial direction R. Planar fins 172 may be mounted at distal ends of corrugations 119. Intake channels 174 may be formed by the spaces or gaps between corrugations 119 and inner edges of planar fins 172. Corrugations 119 may increase the surface area directly exposed to ambient air relative to the example shown in FIG. 3. Eddy currents may also form within corrugations 119 corrugations thereby increasing heat transfer.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. 

What is claimed is:
 1. A heat exchanger, comprising: a cylindrical stator; a cylindrical rotor spaced from the cylindrical stator by a cylindrical gap, the cylindrical rotor configured to rotate relative to the cylindrical stator about a rotation axis; a flattened tube positioned within the cylindrical gap and wrapped on the cylindrical stator, the flattened tube spaced from a surface of the cylindrical rotor that faces the cylindrical gap, a heat transfer fluid flowable through the flattened tube, wherein a shearing liquid zone is defined between the flattened tube and the surface of the cylindrical rotor when the cylindrical gap is filled with a liquid.
 2. The heat exchanger of claim 1, wherein the cylindrical stator is positioned within the cylindrical rotor.
 3. The heat exchanger of claim 2, wherein the cylindrical stator is positioned coaxial with the cylindrical rotor.
 4. The heat exchanger of claim 2, further comprising a motor positioned within the cylindrical stator, the motor coupled to the cylindrical rotor such that the motor is operable to rotate the cylindrical rotor relative to the cylindrical stator.
 5. The heat exchanger of claim 4, wherein a shaft of the motor extends through an end wall of the cylindrical stator along an axial direction, the cylindrical rotor coupled to the shaft of the motor.
 6. The heat exchanger of claim 1, further comprising a plurality of spaced planar fins extending from the cylindrical rotor along a radial direction, the plurality of spaced planar fins defining an axial intake channel extending parallel to the rotation axis through one or more planar fins of the plurality of spaced planar fins.
 7. The heat exchanger of claim 6, wherein the axial intake channel is one of a plurality of axial intake channels, and each of the plurality of axial intake channels extends parallel to the rotation axis through one or more planar fins of the plurality of spaced planar fins.
 8. The heat exchanger of claim 7, wherein each of the plurality of axial intake channels is positioned at a common radial distance from the rotation axis.
 9. The heat exchanger of claim 6, wherein each of the plurality of spaced planar fins is spaced from an adjacent one of the plurality of spaced planar fins by an axial gap, the axial gap being no greater than about twenty-five micrometers.
 10. The heat exchanger of claim 1, wherein the flattened tube is one of a plurality of flattened tubes, each of the plurality of flattened tubes positioned within the cylindrical gap and wrapped on the cylindrical stator.
 11. The heat exchanger of claim 10, wherein the plurality of flattened tubes defines a plurality of parallel flow paths for the heat transfer fluid.
 12. The heat exchanger of claim 1, wherein the shearing liquid zone has a thickness along a radial direction, the thickness of the shearing liquid zone being no less than about one hundredth of an inch and no greater than about one tenth of an inch.
 13. The heat exchanger of claim 1, wherein the flattened tube has a flat surface facing the surface of the cylindrical rotor across the shearing liquid zone.
 14. The heat exchanger of claim 1, wherein the flattened tube is a rolled metal tube.
 15. An appliance, comprising: a cabinet defining a chilled chamber; a heat exchanger positioned within the cabinet, the heat exchanger comprising a cylindrical stator; a cylindrical rotor spaced from the cylindrical stator by a cylindrical gap, the cylindrical rotor configured to rotate relative to the cylindrical stator about a rotation axis; a flattened tube positioned within the cylindrical gap and wrapped on the cylindrical stator, the flattened tube spaced from a surface of the cylindrical rotor that faces the cylindrical gap, a heat transfer fluid flowable through the flattened tube, wherein a shearing liquid zone is defined between the flattened tube and the surface of the cylindrical rotor when the cylindrical gap is filled with a liquid.
 16. The appliance of claim 15, wherein the cylindrical stator is positioned within the cylindrical rotor, and the cylindrical stator is positioned coaxial with the cylindrical rotor.
 17. The heat exchanger of claim 16, further comprising a motor positioned within the cylindrical stator, the motor coupled to the cylindrical rotor such that the motor is operable to rotate the cylindrical rotor relative to the cylindrical stator, a shaft of the motor extending through an end wall of the cylindrical stator along an axial direction, the cylindrical rotor coupled to the shaft of the motor.
 18. The heat exchanger of claim 1, further comprising a plurality of spaced planar fins extending from the cylindrical rotor along a radial direction, the plurality of spaced planar fins defining an axial intake channel extending parallel to the rotation axis through one or more planar fins of the plurality of spaced planar fins, each of the plurality of spaced planar fins spaced from an adjacent one of the plurality of spaced planar fins by an axial gap, the axial gap being no greater than about twenty-five micrometers.
 19. The heat exchanger of claim 15, wherein the shearing liquid zone has a thickness along a radial direction, the thickness of the shearing liquid zone being no less than about one hundredth of an inch and no greater than about one tenth of an inch.
 20. The heat exchanger of claim 15, wherein the flattened tube has a flat surface facing the surface of the cylindrical rotor across the shearing liquid zone. 